Make sure the fabric is not twisted before threading through the rings.
Pull about 1/3 of the length of the sling up through both rings. If the fabric twists while you’re pulling it through the rings, spread it out so the edges stay on the outside, without bunching in the middle. If it’s bunched up, it’s harder to adjust.
Thread the fabric back through the bottom ring. This is easier if you hold the rings apart slightly, especially if the fabric is particularly thick. You may need to pull the hemmed edges outwards while threading to keep them on the outside.
To spread the fabric out in the rings and make it easier to adjust, pull the fabric out about 2" from the rings, and fan it out over your fingers or thumbs. Then pull it back through the rings until it's snug. The hemmed edges should be on the outside. This is an important step whenever you adjust the sling.
Start by deciding which side you want to wear the sling on. Most people use the shoulder of their dominant hand, giving you more freedom of motion on the side the rings sit on. If you have an older baby you carry on one hip more than the other, you may want to position the rings on the opposite side from that hip. Remember to switch sides on a regular basis to minimize fatigue. (You will need to readjust the upper and lower rails when you switch for a safe, comfy carry.)
Hold the rings with the same hand you want the sling shoulder to rest on, with the shoulder seam at the top, tail hanging down from the bottom of the rings. Put your other arm through the loop of the sling.
Bring the sling over your head, keeping the rings close to your shoulder, and guiding your other arm through the sling like a sash. The tail fabric should hang down from the rings in front of you, not loop over the rings towards your back.
Position the rings for comfortable wearing: if they’re too high on your shoulder, the rings will dig into your skin. If they're too low, there's not enough room for the baby in the sling. The top of the rings should be about level with your collarbone.
To avoid discomfort, position the pleated part so the fabric is away from your neck. The pleats will keep it from spreading out too much onto your upper arm. Use a mirror to check that the fabric is also spread out evenly over your back, and reach behind you to pull the lower edge down.
Preadjusting: The closer the sling is to the final snugness, the easier it is to adjust. This also keeps the rings from moving down your chest as you tighten. Put your arm in the sling, elbow towards your center, and tighten the pouch around your arm. Pull the inner edge of the tail to tighten the top, and the outer edge to tighten the bottom.
Always support your child's weight while adjusting the sling, for safety and ease of adjustment!
To loosen a sling quickly, pull up and out on the exposed ring, allowing the fabric to flow more easily. Be sure that you are holding your child with your other hand, since once the tension is off, her weight may allow it to slip.
Adjusting the sling can make the fabric bunch up in the rings, which makes it harder to adjust, and also wedges the rings apart, making it more likely to slip. Whenever you make a major change, take a moment to spread the fabric out in the rings again.
Some fabrics are harder to adjust than others even when the fabric is spread out well in the rings. Use and frequent washing will soften the fabric, but patience is key. Adjust a small section of the sling at a time rather than pulling on the whole tail at once.
The less adjusting you have to do once your baby is in the sling, the better. If you find you need to adjust it once she's in, support her weight with the hand/arm opposite the side the rings are on. The fabric will move easier if her weight isn't also on it.